When cellular telephone technology first appeared in the United States, voice communication channels carried conventional FM modulated signals. Although cellular networks may still support such legacy technology, virtually all of the cellular telephones in use today and almost all of the cell phones being sold today use one form of digital modulation or another.
The technology switchover from analog to digital modulation techniques such as CDMA and GSM accommodated more users but it also paved the way for more services to be provided than would have been possible using analog modulation. Text messaging, camera phone picture transmissions, wireless Internet access, and MP3 and video downloads have all been made possible by digital data transmission.
The nearly ubiquitous cellular coverage, decreasing air time cost and the decreasing cost of cellular handsets has made cellular communications very popular. Some people now forego traditional wire line phone service in their homes, opting instead to rely on cellular communications.
For a variety of reasons, many people now use cell phones for both business and personal communications. Many people now find it necessary to have one phone for business communications and to have a second phone for personal communications. Some employers discourage the use of business phones for personal uses and most people prefer to keep their personal communications private. While using two or more phones may have advantages, most people prefer to carry fewer devices around with them. Using multiple phones requires that extra hardware must be carried about and secured.